Furniture construction



June 17, 1969 w. STEPHENS FURNITURE CONSTRUCTION Sheet Filed March 31, 1967 a 4., INVENTCR. WILL/AM SrEPHE/vs AffOkA/i June 17, 1969 w. I. STEPHENS 3,450,435

FURNITURE CONSTRUCTION Filed March 51, 1967 She et 2 of s H u Q I IY --"'I--" I v 2w 20 52 if: "i

INVENTOR.

Arromv June 17, 1969 w. l. STEPHENS 3,450,435

FURNITURE CONSTRUCTION Filed March 51, 1967 Sheet 3 of s I 50! 50a. 2 20 v. a "W;

INVENTOR. Mum/v 5'7'fPh t'A S ATfO/P/V United States Patent 3,450,435 FURNITURE CONSTRUCTION William I. Stephens, Telford, N.Y., assignor to Art Metal- Knoll Corporation, a corporation of Delaware Filed Mar. 31, 1967, Ser. No. 627,529 Int. Cl. A47c 5/14 US. Cl. 297-446 32 Claims ABSTRACT OF THE DISCLOSURE Furniture construction which uniquely blends a wooden frame with a moldable plastic shell defining the seat and back such that the chair frame and the unitary plastic shell cooperate to stiffen each other whereby a minimum of framework is required.

This invention relates to furniture, and more particularly, to chairs and similar articles of furniture.

The furniture construction envisioned by the present invention comprehends not only side chairs, but arm chairs and lounge chairs, all of which are of extremely simple construction but which provide structural rigidity and comfort for the user.

In the development of modern furniture a number of different approaches have been followed but the basic characteristics of modern furniture construction are simplicity of line along with a marked degree of comfort for the user. Also, modern design has tended to stress a minimum of care of the furniture and durability. Another feature of such design is the ready replaceability for the comfort-providing portions of the furniture. For example, with many pieces of furniture it is intended to be a simple matter to replace the seat and back portions which are subject to great wear.

However, one of the chief objections to much of todays so-called modern furniture is that in its stark simplicity it quite often has an extremely functional appearance and people tend to consider it only suitable for utilitarian purposes and to look upon it with disfavor when considering it from the aesthetic viewpoint.

Accordingly, it is a primary object of the present invention to retain many of the desirable features generally associated with modern furniture design and to enhance its appeal.

Another object is to provide chairs and the like which possess structural strength and durability and yet are extremely pleasing aesthetically.

Another object is to provide furniture that is extremely simple in design and is very readily constructed and assembled.

A fundamental difiiculty that is encountered in furniture construction is the necessity for reconciling the flexibility required for the actual body-supporting seat and back members of the furniture with the demand for simplicity and structural rigidity. Some approaches to providing flexibility have resulted in arrangements such as the provision of a web that is stretched between sidesupporting members. Although the flexible member then affords convenient replaceability, it does not contribute significantly to the structural strength needed for the chair frame so that the frame per se must be extremely rigid in construction, and this necessitates that the frame include a plurality of cross pieces or bracing members extending from one side of the chair frame to the other. Other types of constructon known in the prior art, while affording good structural rigidity, provide so at the expense of comfort and it is quite frequently the case that extra heavy cushion means must be provided for the users comfort.

One of the important features of the present invention resides in the unique blending of the desirable qualities imparted to furniture construction by wood grain with the moldable characteristics of synthetic materials such as plastic. The wood grain characteristics are considered of fundamental importance in the appeal to most peoples aesthetic sensibilities. Furthermore, the chair resulting from the unique blending is one not only having great structural strength, and therefore durability, but also, with greatly facilitated replaceability at minimum expense of the comfort-providing portions of the chair. The structural strength possessed by the chair construction of the present invention stems from the fact that the chair frame, which is constituted of wooden members, and the unitary seatand-back plastic shell cooperate to stiffen each other, whereas individually, they are quite flexible. In the construction of a chair, for example, the unitary plastic shell is molded so that its contours ideally fit the contours of the chair frame such that the plastic shell is readily secured at a significant extent of its total perimeter. Because of the contour of the plastic shell the body of a user is accommodated with a great degree of comfort; that is to say, although the plastic shell affords the aforenoted rigidity of structure when secured to the chair frame, it is resilient enough to yield under load. Moreover, this resilience is supplemented by the fact that the plastic shell, in accordance with a preferred form of the present invention, is covered by a layer of foam rubber and in turn this layer of foam rubber is completely covered by a fabric so as to result in an attractive seat and back for the chair. When the fabric becomes soiled or worn, it can be simply removed, as will be explained hereinafter, and can be inexpensively replaced. Moreover, such replacement can be accomplished without return of the chair to the factory. Thus, the flexible shell forming the seat and back for the chair is retained in place and only the fabricand possibly the foam rubberneed be replaced.

An ancillary feature to the construction described above resides in the manner of attaching the aforenoted upholstery, i.e. the foam rubber pad and fabric combination that serves as a covering and cushioning means for the plastic shell. In accordance with one version of this feature, the pad and its associated fabric are attached to the inner side of the shell before the shell is secured to the wooden frame. However, a small margin of approximately one inch is left outside of a groove which extends around the periphery of the shell. This groove is adapted to receive the securing means, for example, in the form of staples, for securing the shell to the frame. The margin of foam rubber is left unglued in this version and is simply peeled back, to expose the aforenoted groove, when it is desired to secure the shell to the frame. After the shell has been secured the fabric margin that remains, i.e. the loose fabric edge, is tucked in under the edge of the plastic shell which is defined by a flange-like portion extending beyond the groove. This arrangement, of course, makes for very quick and easy assembly and is directed to achieving easy replaceability of the fabric covering as previously noted. Furthermore, this arrangement has the advantage that no welts or other means must be employed to cover up loose fabric edges and, in addition, the securing means are completely hidden from view thereby adding to the finished appearance of the chair.

In accordance with a preferred version of the ancillary feature of upholstery attachment, the plastic shell is secured to the Wooden frame prior to covering the inner side of the shell with the upholstery pad and fabric combination. Thus, only the outer side of the plastic shell is covered with a suitable fabric and then the plastic shell is secured in the previously described manner by the use of staples to the chair frame. Thereafter, the foam rubber pad is glued or cemented to the inner side of the shell and the loose fabric edge, as before, is tucked in under the flange-like portion of the plastic shell.

The usual procedure, in connection with the aforedescribed attachment of the foam rubber pad and fabric combination to the inner side of the plastic shell, is to secure a piece of fabric to the outer or back side of the shell. However, an alternative method would be to use a shell that is textured and colored so that it would be suitable for installation without the necessity for covering its outer side.

Briefly described, the chair of the present invention involves the construction of a framework consisting of two side sections that, except at the back-supporting region, are tied or connected together by only a single cross member. This cross member is located such that it appears to define the margin of the forwardly extending extremity of the plastic shell. In other words, it appears to blend with the plastic shell and thereby contributes to the aesthetically pleasing look of the chair. Each of the side sections comprises two basic parts or members, one of which defines a rear leg for the chair. In its extension upwardly, this part contributes to forming the backsupporting rail or edge member. The other part or member of each section provides a front leg for the chair and is so constructed that it cooperates with the first part in defining the back-supporting edge member. In a preferred embodiment of the chair construction the second part is constructed specifically to define a horizontal seat-supporting rail, whereas in an alternative embodiment, the horizontal portion defines a support which makes contact with a flange on the plastic shell and the actual seatsupporting portion of the plastic shell is suspended therefrom.

The only cross member that is used for connecting the legs of the chair frame is a member extending from one of the front legs to the other and it is so positioned so that it extends horizontally at a point just below the lowermost portion of the shell member forming the chair seat. It is advantageously positioned inwardly of this lowermost portion whereby no contact of the user with this cross member is possible.

It will be appreciated then that an important aspect relating to this provision of only a single cross or bracing member for connecting the legs is that the chair is greatly simplified in that the framework is reduced to a bare minimum. Beyond such reduction in the framework is the fact that the chair is free standing, which is a way of saying that there are no readily apparent cross members which would add to the bulky look of the chair.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawmgs.

FIG. 1 is a front perspective view of a preferred embodiment of a chair in accordance with this invention.

FIG. 2 is a rear perspective view showing the arm rest removed from the chair frame.

FIG. 3 is a side view of the chair.

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 3.

FIG. 5 is a sectional view taken on the line 5-5 of FIG. 3.

FIG. 6 is an enlarged sectional view taken on the line 6--6 of FIG. 3.

FIG. 7 is an enlarged view taken on the line 7--7 of FIG. 5.

FIG. 8 is an enlarged sectional view illustrating the step of securing the shell to the chair frame.

FIG. 9 is an enlarged sectional view showing the step of tucking in a fabric.

FIG. 10 is an exploded view showing the several parts of the chair of the present invention.

FIG. 11 is a rear perspective view of a modification in the securing of the plastic shell to the chair frame.

FIG. 12 is an enlarged sectional view taken on the line 12-12 of FIG. 11.

FIG. 13 is an exploded view showing the parts of another embodiment of a chair in accordance with the present invention.

FIG. 14 is a fragmentary view of a portion of the chair frame to show the construction of the laminated Wood stock of which the chair frame is formed.

Referring now to the drawing, and specifically to the FIGURES 1-10 and 14, the chair construction comprises a framework 10 which is formed of laminated wood stock which, as is well-known, provides good structural strength and stability. What is meant by the term stability in this context is that a bent or curved piece is in its normal shape when finished. Thus, in fabricating the chair frame members, and more particularly, in fabricating the side sections, a panel of considerable width, having separate veneers with bonding means between them, is placed in a press. This laminated panel is curved between formed blocks or dies as the press closes; then, the pressure in the press holds the veneers in intimate contact while heat polymerizes the bonding agent. The result is that a curved laminated panel is removed from the press. The panel will remain in this shape. The frame members are cut transversely from these panels and are of sufficient thickness to form the legs and rails of the chair. Notably, each of the frame members has great strength because all, or substantially all, of the constituent veneers run the length of the frame member.

The above-noted advantages of the laminated wood stock construction can be appreciated by particular reference to FIGS. 1 and 14. There it will be seen that each of the side sections of the chair frame work 10 consists of the two basic parts or frame members designated 12a and 12b. A fragment of the part 12b is shown broken away in FIG. 14 to illustrate the fact that the constituent veneers of the laminated wood stock forming this part 12b have been fashioned so that their individual grains all run in their same direction and extend the entire length of this part 12b. Not only do the parts 12a and 12b posses great structural strength in and of themselves because of their aforedescribed fabrication, but they are joined together in such a manner as to retain such strength for the entire side section. The parts 12a form the rear legs 14 for the chair, while the parts 12b define the front legs 18 for the chair and the seat-supporting side rails 19. Together, these parts form the back-supporting edge members 16. The contacting portions of parts 12a and 12b in so defining these edge members are joined together by a well-known gluing process. It will be appreciated that this gluing together extends over a considerable distance and consequently contributes significantly to the goal of great structural strength for these side sections. The h-shaped side sections thus strongly resemble the branches of a tree joined together to form a common bough and contrast sharply with the product of conventional techniques of joining frame members of this type, such as mortice and tenon arrangements, which, because of their nature, are not capable of providing the structural strength resulting from the described method of joinder.

The side sections of the chair framework 10 are joined together by the cross piece or bracing members 20 and 22. The bracing member 22 is connected at the top of the chair back and is joined to the edge member 16 by a mortice and tenon arrangement. Similarly, the bracing member 20 extends from one side section to the other and is located so as to join the legs 18. This is also accomplished typically by a mortice and tenon arrangement.

The basic framework of a side chair in accordance with the present invention is now complete, with only the aforedescribed components. However, for an arm chair the same basic framework is utilized, and arm rests 24 are provided. They are in a generally rectangular shape and are formed by two separate pieces suitably joined together, as can be appreciated by reference to FIG. 3. Each arm rest 24 is attached to its respective side section by the use of a plurality of threaded connectors 26 received in holes provided in the framework. The lower horizontal portion of the arm rests 24 are aligned with the horizontal run of the part 12b which form the side rails 19 and are spaced from the rails 19 by the spacers 21.

The framework 10, having a minimum of wooden frame members, is not perfectly rigid and would not normally serve in and of itself for general chair purposes. However, this frame construction is combined with a plastic shell as will now be described. The plastic shell shown and designated 50 provides the actual load bearing surfaces of the seat and back of the chair. This plastic shell 50 is of unitary construction and typically it is vacuum formed, or injection molded, and is preferably constituted of polyethylene or similar synthetic resin material. This material has the quality of being somewhat flexible, that is, of being resilient and capable of deformation when loaded. However, the plastic shell 50 is rigid enough so that when it is secured to the framework it cooperates therewith to produce an extremely rigid chair.

The plastic shell 50 is contoured to fit the body of the user and its contour is matched to the contour of the framework 10 so that the shell 50 may be secured throughout substantially its entire perimeter. The plastic shell 50 is dish-shaped through most of its length, as may best be appreciated by reference to FIG. 5, so that it has a central concave portion 50a as seen in that figure and a flange-like portion 50b at which the shell 50 is secured to the framework. However, at its longitudinal extremities, that is, at the top section 500 of the portion forming the back of the chair, and at the forward section 50d of the portion forming the seat, there is no concavity.

It will be particularly noted by reference to the side elevation of FIG. 3 that the plastic shell 50 has a very straight profile except for the flaring outwardly of the upper portion of the back of the chair, and the flaring downwardly at the forward portion of the seat. Where it flares downwardly, it meets the bracing member 20 and its curvature thereat, that is, its downward curvature from one side of the chair to the other matches very closely the downward curvature of the bracing member 20. In appearance, then, the bracing member 20 does not stand out as a separate element and seems to form part of the chair seat.

It will be particularly noted that the portions of the plastic shell 50 which define the seat and back of the chair are united by an arcuate section 50x. This arcuate section 50x finds its counterpart in the chair framework. Thus, the part 12b of the chair framework has an arcuate section 23 which joins the side rail 19, defined by the horizontal run of the part 1217, with the upwardly extending portion 25 of part 12!) that meets with a matching portion 27 so as to define together the backsupporting edge 16.

In the assembly of the chair of the present invention a cushioning means is aflixed to one side, i.e. the inner side of the shell that will be in contact with the users body. This cushioning means is a supplement to the comfort provided by the flexibility of the shell 50. The cushioning means consists of a layer 52 of foam rubber or like material. The layer of foam rubber is covered with a layer of fabric 54 and the fabric is extended so as to cover the outer side of the plastic shell 50'. The complete coverage of the plastic shell by the fabric 54 yields a very attractive finish for the chair. However, as noted previously, the shell need not be completely covered if the back side has a suitably attractive finish as is.

As can best be seen in FIG. 8, a technique in accordance with a specfic feature of the present invention is utilized for the securing of the shell 50 and for the securing of the cushion and fabric combination. As can clearly be seen in FIG. 8, the fabric 54 is in contact with the outer surface 500 and is conventionally adhered thereto by gluing, for example. The edge of the fabric 54 in contact with the outer surface 500 is seen to terminate in the space between the shell 50 and the framework 10. A typical point of securing the shell 50 to the framework 10 is illustrated here, and either version of the upholstery attachment feature may be applied. That is to say, either the preferable way of first securing the shell to the framework may be followed, or the alternative way of first gluing the foam rubber to the inner side of the shell. In the first case, the staple gun 58 would be brought to bear before the foam rubber 52 is brought into actual contact with the shell 50. The staple gun 58 is, of course, used to drive the staples 56 into the groove 50) and thence into the framework 10. Then, the entire foam rubber fabric combination is glued to the shell. The loose edge of the fabric 54 is tucked in under the shell 50, typically by means of a spatula 60 as shown in FIG. 9.

In the alternative case, most of the foam rubber is already glued to the shell before the staples are driven. A margin of approximately to 1 inch which has not been glued is then peeled back to allow for a-ffixing the staples. Then, after securing the shell around its entire perimeter, glue is applied to the margin of the foam rubber and to the loose edge of the associated fabric 54 and, as before, this loose edge is tucked under the shell 50. It will be appreciated that the alternative technique necessitates a two-stage gluing operation, whereas the preferred technique involves only one.

Referring now to FIGS. 11 and 12 there is illustrated an alternative embodiment of a chair comprising a wooden framework and a plastic shell. The same numerals as were used with the preferred embodiment refer to like parts in the alternative embodiment. The essential difference from the preferred embodiment is that in this alternative embodiment the injection-molded plastic shell 50 is itself provided with the securing means. Thus, the shell is formed with hollow lugs 50g spaced around its erimeter. Alternatively, a continuous rib may be provided around all, or most, of the perimeter. These modifications of the shell use no molded foam rubber. In other words, the foam rubber-fabric combination that was previously used is dispensed with and comfort is provided by the shell itself.

As before, the plastic shell 50 is concave throughout most of its length except for the top section 500 of the chair back and the forward section 50d of the chair seat. However, the concavity in the chair back and seat is much shallower, as can be seen by reference to FIG. 12 which best illustrates the central region of the shell 50, i.e. region 50a. The shell 50 in this instance is secured to the chair framework 10 by fitting the lugs 50g into appropriately spaced holes 62 provided in the frame work 10. The lugs 50g are, of course, glued into holes 62 for firm fastening of the shell 50 thereto. Similarly, if ribs are used they would be glued in a slot provided in the framework.

Referring now to FIG. 13, there is shown a completely distinct version of the chair of the present invention which utilizes the same principle heretofore described, i.e. of a minimum wood structure combined with a vacuumformed plastic shell. But the configuration for the framework is totally different and the vacuum-formed shell likewise has a totally different configuration so as to conform to the configuration of the framework. The basic difference in the chair of FIG. 13 is that the side rails 19 formed by the horizontally-extending portion of the basic part 12b are at a higher level so as to constitute, in effect, arm rests. However, the same function as before is served by the side rails 19, that is, they support the plastic shell 50. The topmost portion 500 and the forwardmost portion 50d of the plastic shell have substantially the same shape as in the first embodiment. However, the plastic shell 50 is generally more in the shape of a bucket whose portion forming the seat for the chair has sides 50j. Outwardly extending flanges 50k are provided, and in their runs from the top of the chair back to the forwardmost portion of the chair seat they extend over the corresponding portions of the framework 10. Thus, the flanges slope downwardly corresponding to the downward slope of the edge support 16 and then generally horizontally over the side rails 19, and then downwardly again at the legs 18. Thereby the entire perimeter of shell 50 may be secured to the chair framework 10 and the essential advantages of structural rigidity with the free-standing appearance for the chair are again realized.

This alternative embodiment of FIG. 13, of course, has the additional advantage that it has ready-made application as an arm chair without the necessity of affixing additional elements to the basic framework, but of course, it does not have the flexibility of the preferred embodiment which can be readily applied in either mode that is, as either a side chair or arm chair.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. A chair construction comprising a wooden framework having a pair of side sections, each section comprising first and second frame members, the first frame member completely defining a rear leg, the second member completely defining a front leg and a side rail, the first and second members being joined together so as to define a, back-supporting edge for said chair; a first bracing member connecting said side sections and joined thereto at the top of the chair back, another bracing member extending between said side sections so as to join the front legs; a unitary molded plastic shell defining the seat and back for the chair, said plastic shell being secured substantially along its entire perimeter to the framework; said first and second frame members being constituted of laminated wood stock, substantially all of whose layers have their grains running the entire length of each frame member.

2. A chair construction as defined in claim 1, wherein said plastic shell is concave along most of its length and wherein said plastic shell flares outwardly at the top of the chair back, and flares downwardly at the forward portion of the chair seat.

3. A chair construction as defined in claim 1, wherein said plastic shell includes a flange-like portion for securing said shell along its perimeter to the chair framework.

4. A chair construction as defined in claim 2, wherein said plastic shell is secured at the top of the chair back to the first bracing member and at the forward portion of the chair seat to the other bracing member.

5. A chair construction as defined in claim 3, wherein said plastic shell is also secured to the side rails and to the back-supporting edges.

6. A chair construction as defined in claim 2, wherein the plastic shell is secured at the plurality of spaced points along its perimeter to the chair framework by means of staples located within grooves formed in said flange-like portion of said shell.

7. A chair construction as defined in claim 6, where in a foam rubber pad is secured to the inner side of said plastic shell and the plastic shell is covered with a fabric on both its inner and outer sides.

8. A chair construction as defined in claim 1, including arm rests secured to the chair framework.

9. A chair construction as defined in claim 8, wherein said arm rests are generally rectangular in shape and are secured at their lower horizontal run to the side rails.

10. A chair construction as defined in claim 1, wherein said side rails define the arm rests of said chair.

11. A chair construction as defined in claim 1, wherein said plastic shell is bucket-shaped and has side portions.

12. A chair construction as defined in claim 1, wherein said side rails extend horizontally at a height corresponding to an arm rest position.

13. A chair construction as defined in claim 1, wherein said plastic shell is injection-molded and includes a series of integral lugs spaced about the perimeter of said shell.

14. A chair construction as defined in claim 13, wherein said chair framework includes holes into which said lugs are fitted.

15. A chair construction comprising a pair of wooden side sections, each side section being constituted by two frame members, the first frame member completely defining a rear leg, the other member completely defining a front leg and a side rail, the two members being joined together to define a back-supporting edge for said chair; a unitary molded plastic shell defining a seat and back for the chair, said shell being generally dish-shaped and having a marginal flange-like portion extending around the entire perimeter of said shell, said marginal portion including a groove for receiving means for securing said shell to the chair framework.

16. A chair construction as defined in claim 15, wherein said plastic shell is concave along most of its length and wherein said plastic shell flares outwardly at the top of the chair back, and flares downwardly at the forward portion of the chair seat.

17. A chair construction as defined in claim 15, wherein said plastic shell includes a flange-like portion for securing said shell along its perimeter to the chair framework.

18. A chair construction as defined in claim 16, wherein said plastic shell is secured at the top of the chair back to the first bracing member and at the forward portion of the chair seat to the other bracing member.

19. A chair construction as defined in claim 17, wherein said plastic shell is also secured to the side rails and to the back-supporting edges.

20. A chair construction as defined in claim 6, wherein the plastic shell is secured at a plurality of spaced points along its perimeter to the chair framework by means of staples located Within grooves formed in said flange-like portion of said shell.

21. A chair construction as defined in claim 20, wherein a foam rubber pad is secured to the inner side of said plastic shell and the plastic shell is covered with a fabric on both its inner and outer sides.

22. A chair construction as defined in claim 15, including arm rests secured to the chair framework.

23. A chair construction as defined in claim 22, wherein said arm rests are generally rectangular in shape and are secured at their lower horizontal run to the side rails.

24. A chair construction as defined in claim 15, wherein said side rails define the arm rests of said chair.

25. A chair construction as defined in claim 15, wherein said plastic shell is bucket-shaped and has side portions.

26. A chair construction as defined in claim 15, where in said side rails extend horizontally at a height corresponding to an arm rest position.

27. A chair construction as defined in claim 15, where-' in said plastic shell is injection-molded and includes a sirileis of integral lugs spaced about the perimeter of said s e 28. A chair construction as defined in claim 27, wherein said chair framework includes holes into which said lugs are fitted.

29. A method of attaching upholstery to a chair, said chair comprising a wooden framework and a unitary molded plastic shell defining the seat and back for the chair, comprising the steps of securing an upholstery pad to the inner side of said shell, said upholstery pad having a marginal portion extending around the perimeter of said shell and being adapted to cover a flange-like member, having a groove, defining the edge of said shell; bringing said plastic shell into contact-at its flange-like member with the chair framework; affixing securing means at spaced points along said groove into the chair framework; and covering the flange-like member with the marginal portion of said pad.

30. A method of attaching upholstery as defined in claim 29, wherein said upholstery pad is initially secured to the inner side of said shell with a marginal portion left unsecured, said plastic shell is thereafter brought into contact at its flange-like member with the framework and the marginal portion of the upholstery pad is lifted so as to expose said groove, and, thereafter, said marginal portion of said pad is secured so as to cover said flange-like member.

31. A method of attaching upholstery as defined in claim 29, including the further steps of covering the pad with a fabric and tucking in the edges of the fabric under the flange-like member.

10 32. A method of attaching upholstery as defined in claim 29, comprising the further step of securing a layer of fabric to the outer side of said shell.

References Cited UNITED STATES PATENTS 2,726,713 12/1955 Turner 297447 X 3,152,836 10/1964 Swan 297445 3,188,663 6/1965 Conrad 297452 X 3,300,251 1/1967 Helms 29'7-452 X 3,318,635 5/1967 Barecki et a1. 297445 X 3,328,084 6/1967 Whitener et a1. 297418 X FOREIGN PATENTS 667,316 2/1952 Great Britain.

825,376 12/1959 Great Britain. 1,080,366 8/ 1967 Great Britain.

CASMIR A. NUNBERG, Primary Examiner.

US. Cl. X.R. 

